1. Field of the Invention
The invention relates to an apparatus and a method for stretching a weft thread inserted into a weaving shed, in particular for air-jet weaving machines.
Weft threads are inserted into a weaving shed at high speeds. Because of the driving forces and because of the braking forces at the end of the weaving insertion, the weft threads become elastically elongated. Because of this elongation, the weft threads have the tendency, after the end of the weft insertion, to snap back into the shed and to form loops or snarls there. Such snarls or loops result in weave faults. To prevent the weft thread from snapping back, so-called stretching nozzles are typically disposed on the side of the shed opposite the insertion side. They are using an air stream, tension the inserted weft thread and keep it stretched. This tensioning and stretching can be further improved by keeping so-called auxiliary blow nozzles or relay nozzles activated for a certain time after the weft insertion. For exerting a sufficient force for the stretching a relatively long length of weft thread must be taken up by the stretching nozzle. Moreover, the air consumption of a stretching nozzle of this kind is relatively high.
2. Related Art
The object of the invention is create an improved device for keeping an inserted weft thread tensioned or stretched.